关键词: 恶性疟原虫, 二氢叶酸还原酶(dhfr)基因, 基因突变

Abstract: 　Objective To investigate the gene point mutation in the dihydrofolate reductase thymidylate synthase (dhfr) gene of Plasmodium falciparum isolate from Yunnan Province strongly associated with pyrimethamine and cycloguanil resistance. Methods Nested PCR and restriction endonuclease digestion were applied to detect the gene mutation using dried blood filter paper collected from the fields in Yunnan Province. Results Different mutations were found in 4 amino acids at positions 16, 51, 108 and 164 of dhfr gene, particularly, Asn 108 and Ile 51, the mutaiton frequency being 94.1% and 90.1%, respectively. The frequency of the wild type genotype (3D7 type) Ser 108 appeared lower ( 9.1%) , while the frequency of the Ala 16 was high( 61.8%); the mutation type was very high, the ratio of HB3 type, 7G8 type/FCR3 type and Cambodian type was 1∶21∶7.5. Conclusion The investigation first demonstrated that Plasmodium falciparum Yunnan isolate dihydrofolate reductase thymidylate synthase gene(dhfr) at positions 16, 51 ,108 and 164 exhibited different degrees of point mutation. The frequency of mutation of the 7D8 type involved in pyrimethamine resistance was higher, while that of the FCR3 type involved in cycloquanil resistance was lower.

Key words: Plasmodium falciparum, dihydrofolate reductase thymidylate synthase (dhfr)gene, gene mutation